The objective of the thesis was to investigate for the presence of changes in cortical sensorimotor processes (corticospinal excitability and the body schema measured with the Left Right Judgment Task (LRJT) performance), in participants with Musculoskeletal Disorders (MSD) of the wrist/hand. A second objective was to determine the relationship between these cortical sensorimotor processes and measures of sensory and hand motor function, disability, pain and pain related psychosocial factors.
First, an observational cross-sectional study was conducted to explore corticospinal excitability of muscles in the hand and cortical sensorimotor processes, utilizing transcranial magnetic stimulation and the LRJT in healthy, pain-free participants and participants with chronic wrist/hand pain. Increased corticospinal excitability for the abductor pollicis brevis of the affected hand in participants with chronic MSD of the wrist/hand was found and these changes were significantly correlated with pain intensity, disability, and negatively correlated with spinal motoneuronal excitability. Differences in LRJT performance were also found between healthy control participants and participants with pain for both LRJT accuracy and reaction time.
In a second cross-sectional study, LRJT performance, motor, sensory and cognitive assessments were performed on sixty-one participants with MSD of the right dominant wrist/hand. The multiple linear regression model revealed that taking pain medication, participating in (social, work, household and leisure) activities, two-point discrimination, and motor performance explained performance on the LRJT of the right (affected) hand. Those participants that took pain medication on the day of the evaluation performed more poorly on both LRJT accuracy and reaction time of the right (affected) hand. These participants had higher pain severity and disability scores and decreased cognitive and motor function.
Collectively, these results suggest that participants with heterogeneous MSD of the wrist/hand display altered cortical sensorimotor processes. Whereas corticospinal excitability appears to be related to pain intensity and disability, the LRJT may be associated with a confluence of factors (sensory, motor, cognitive-affective, and behaviours). These findings suggest that cortical sensorimotor changes do not simply appear to be the result of the condition but involve a complex interaction between pain, sensorimotor and cognitive-affective processes, and possibly behavioural responses to the condition. The findings also provide valuable insight as to those persons who may benefit from cognitively directed interventions in addition to peripherally driven rehabilitative treatments.